1. Field of the Invention
The present invention relates to an imaging lens, an optical apparatus equipped with the imaging lens, and a method for manufacturing the imaging lens.
2. Related Background Art
In an optical system capable of carrying out excellent optical performance from infinity to a close object, there have been proposed various lens types such as, for example, a four-lens-group configuration disclosed in, for example, Japanese Patent Application Laid-Open No. 2009-063715, and a two-lens-group configuration disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-086308. Regarding such an optical system capable of realizing excellent optical performance upon focusing from an infinity object to a close object, request for suppressing ghost images and flare, which deteriorate optical performance, as well as aberrations become increasingly strong. Accordingly, a higher optical performance is required to an antireflection coating applied to a lens surface, so that in order to meet such request, multilayer design technology and multilayer coating technology are continuously progressing (for example, see Japanese Patent Application Laid-Open No. 2000-356704).
However, in the four-lens-group configuration, because of the large number of the lens group the optical system tends to become large. Moreover, in the two-lens-group configuration, although the optical system can easily be downsized, a moving amount necessary for focusing becomes large. At the same time, there has been a problem that reflection light producing ghost images and flare tends to be generated from optical surfaces of such an imaging lens.